The invention relates to conductive layers and fabrication methods thereof and, more particularly, to methods for fabricating high conductive layers at a relatively low curing temperature.
Typically, the thermal resist temperature or operative temperature for fabricating a conductive layer on substrates of conventional electronic products is less than 350° C. for polyimide substrates, 290° C. for printed circuit boards (PCBs), and lower than 200° C. for other plastic substrates. The curing temperature of conductive pastes for conventional low temperature products are constrained to the thermal resist temperature or operative temperature of the substrates. The resistivity of the conductive layer such as silver on the substrate is 10–50 times that of pure silver, resulting in more power consumption, signal loss, and reduction of transmission distance during signal transmission.
U.S. Pat. No. 6,036,889 (Kydd et. al.), the entirety of which is hereby incorporated by reference, discloses a method of fabricating a metal layer. A conductive paste comprising organic acidic salt and metal flakes is formed on a substrate. The organic acidic salts such as silver 2-ethylhexanoate (C8H15O2Ag) are decomposed at 250–350° C. to create interlinks between the metal flakes, thereby improving conductivity of the metal layer. Moreover, U.S. Pat. No. 6,036,889 (Kydd et. al.), the entirety of which is hereby incorporated by reference, further discloses a method of fabricating a metal layer. Organic acidic salts such as silver 2-ethylhexanoate (C8H15O2Ag) are decomposed at 250–350° C. to create interlinks between nanometer colloidal metal flakes, thereby improving conductivity of the metal layer.
The decomposition temperature of conventional organic acidic salts, however, is still relatively high, and cannot be held under 200° C. for use in fabrication of conductive layers on plastic substrates.